Electric motor driven turbine fluid pumps are customarily used in fuel systems of an automotive vehicle and the like. These pumps typically include an external sleeve which surrounds and holds together an internal housing adapted to be submerged in a fuel supply tank with an inlet for drawing liquid fuel from the surrounding tank and an outlet for supplying fuel under pressure to the combustion engine. A downward projecting shaft of the electric motor concentrically couples to and drives a disk-shaped pump impeller having an array of circumferentially spaced vanes disposed about the periphery of the impeller. An arcuate pumping channel carried by the housing substantially surrounds the impeller periphery and extends from an inlet port and to an outlet port at opposite ends. Liquid fuel disposed in pockets defined between adjacent impeller vanes and the surrounding channel develops pressure through a vortex-like action induced by the three dimensional profile of the vanes and the rotation of the impeller.
The vanes of disk-shaped turbine pump impellers have a wide variety of three-dimensional profiles or shapes. This shape is dependent upon the type of disk impeller utilized and the surrounding housing of the pump. For example, fuel pump impeller vanes are known to be generally flat, straight and radially outwardly extending. Other impeller vanes are known to be flat, straight and canted relative to a radius of the impeller. Yet other vane designs, such as that described in U.S. Pat. No. 6,113,363 which issued to Talaski on Sep. 5, 2000 and is incorporated herein by reference, have vanes which are inclined such that the tip trails the base as the impeller rotates and are generally arcuate along both their axial and radial extent.
There are generally two types of disk-shaped turbine pump impellers which can dictate the profile of an impeller vane. They are generally referred to as a guide ring-type and a hoop-type.
A guide ring-type impeller configuration is utilized in conjunction with a stationary guide ring firmly mounted to the housing of the pump. The guide ring functions to divert the fuel flow from a vertical inlet port, guides the fuel through a substantially horizontal arcuate or annular channel, then strips the fuel from the moving impeller vanes within the annular channel and diverts the fuel to a substantially vertical outlet port. The arcuate channel extends about the periphery of the guide ring-type impeller, between the inlet and outlet ports by about 270 to 330 degrees, and is defined radially outwardly by the guide ring and radially inwardly by the periphery of the impeller. The vanes, such as those described in the '363 patent, have free ends or tips which project substantially radially outward from the impeller and laterally into the channel. A stripper portion of the guide ring is diametrically opposed to the channel and orientated circumferentially between the inlet and outlet ports. As the impeller rotates, the moving tips of the vanes brush closely to the stripper portion of the guide to strip the pressurized fuel from the impeller and divert it from the channel to the outlet port. The stripper portion must maintain its closed orientation to the tips of the vanes to prevent bypass of pressurized fuel from the outlet port to the low pressure inlet port. This stripping relationship between the guide ring and free-ends or tips of the impeller vanes requires expensive precision in manufacturing, can wear over time degrading the efficiency of the pump, and requires extra parts which may further increase the cost of manufacturing and maintenance.
A hoop-type impeller, such as that illustrated in U.S. patent application Publication No. U.S. 2002/0021961 A1 published Feb. 21, 2002 and issued to Pickelman et al., and in U.S. Pat. No. 5,807,068 (FIGS. 6 and 7) issued Sep. 15, 1998 to Dobler et al., both of which are incorporated herein by reference, does not utilize a guide ring but instead has a peripheral hoop as a unitary part of the impeller. The hoop is engaged to and supported by the radially outward ends of the circumferential array of impeller vanes. Impeller pockets defined circumferentially between the adjacent vanes communicate only laterally outward from the impeller into upper and lower grooves of the channel defined by the pump housing. In designs with an impeller hoop, communication between the impeller pockets and the channel, is solely axial, or side-flanking. Unfortunately, the known three-dimensional vane profiles for the hoop-type impeller are limited and overall pump efficiencies are relatively low.
Known turbine fuel pumps have an overall efficiency of approximately 35–45%, and when combined with an electric motor having a 45–50% efficiency, the overall efficiency of such electric motor turbine fuel pumps is between about 16–22%. Moreover, higher flow and pressure requirements for automotive vehicle fuel pumps are exceeding the capabilities of conventional 36–39 mm diameter regenerative turbine pumps. To increase fuel output and pressure, pumps must operate at higher speeds. However, this may result in cavitation, which continues to be a challenge. Thus, there is a continuing need to improve the design and construction of such fuel pump impellers to increase their efficiency.